Add X86 target support for NuttX

* Implement `i686-unknown-nuttx` and `x86_64-unknown-nuttx` target definitions
* Integrate new targets into the platform support documentation
* Update tests to include new target revisions

This change introduces support for 32-bit and 64-bit x86 architectures on the NuttX operating system, enhancing the range of platforms Rust can target. The targets are defined as tier 3, indicating that they are supported but not automatically tested by the Rust project. The `i686-unknown-nuttx` target uses the `pentium4` CPU and 32-bit pointers, while the `x86_64-unknown-nuttx` target uses the `x86-64` CPU and 64-bit pointers. Both targets disable dynamic linking and use inline stack probes for improved performance and reliability in a bare-metal environment.

Additionally, this commit updates the platform support documentation to list the new targets and includes them in the test suite to ensure that they build correctly.

Signed-off-by: Huang Qi <[email protected]>

Author: no1wudi

compiler/rustc_target/src/spec/mod.rs

@@ -1977,6 +1977,8 @@ supported_targets! {
 
     ("x86_64-unknown-linux-none", x86_64_unknown_linux_none),
 
+    ("i686-unknown-nuttx", i686_unknown_nuttx),
+    ("x86_64-unknown-nuttx", x86_64_unknown_nuttx),
     ("thumbv6m-nuttx-eabi", thumbv6m_nuttx_eabi),
     ("thumbv7a-nuttx-eabi", thumbv7a_nuttx_eabi),
     ("thumbv7a-nuttx-eabihf", thumbv7a_nuttx_eabihf),

compiler/rustc_target/src/spec/targets/i686_unknown_nuttx.rs

@@ -0,0 +1,36 @@
+use crate::spec::{Cc, LinkerFlavor, Lld, StackProbeType, Target, TargetOptions, cvs};
+
+pub(crate) fn target() -> Target {
+    let mut base = TargetOptions {
+        os: "nuttx".into(),
+        dynamic_linking: false,
+        families: cvs!["unix"],
+        no_default_libraries: true,
+        has_rpath: false,
+        position_independent_executables: false,
+        relro_level: crate::spec::RelroLevel::Full,
+        has_thread_local: true,
+        use_ctors_section: true,
+        ..Default::default()
+    };
+    base.cpu = "pentium4".into();
+    base.max_atomic_width = Some(64);
+    base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-m32"]);
+    base.stack_probes = StackProbeType::Inline;
+
+    Target {
+        llvm_target: "i686-unknown-nuttx".into(),
+        metadata: crate::spec::TargetMetadata {
+            description: Some("NuttX/x86".into()),
+            tier: Some(3),
+            host_tools: Some(false),
+            std: Some(true),
+        },
+        pointer_width: 32,
+        data_layout: "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-\
+            i128:128-f64:32:64-f80:32-n8:16:32-S128"
+            .into(),
+        arch: "x86".into(),
+        options: base,
+    }
+}

compiler/rustc_target/src/spec/targets/x86_64_unknown_nuttx.rs

@@ -0,0 +1,40 @@
+// Generic x86-64 target for bare-metal code - Floating point disabled
+//
+// Can be used in conjunction with the `target-feature` and
+// `target-cpu` compiler flags to opt-in more hardware-specific
+// features.
+
+use crate::spec::{StackProbeType, Target, TargetOptions, cvs};
+
+pub(crate) fn target() -> Target {
+    let mut base = TargetOptions {
+        os: "nuttx".into(),
+        dynamic_linking: false,
+        families: cvs!["unix"],
+        no_default_libraries: true,
+        has_rpath: false,
+        position_independent_executables: false,
+        relro_level: crate::spec::RelroLevel::Full,
+        has_thread_local: true,
+        use_ctors_section: true,
+        ..Default::default()
+    };
+    base.cpu = "x86-64".into();
+    base.max_atomic_width = Some(64);
+    base.stack_probes = StackProbeType::Inline;
+
+    Target {
+        llvm_target: "x86_64-unknown-nuttx".into(),
+        metadata: crate::spec::TargetMetadata {
+            description: Some("NuttX/x86_64".into()),
+            tier: Some(3),
+            host_tools: Some(false),
+            std: Some(true),
+        },
+        pointer_width: 64,
+        data_layout:
+            "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128".into(),
+        arch: "x86_64".into(),
+        options: base,
+    }
+}

src/doc/rustc/src/platform-support.md

@@ -314,6 +314,7 @@ target | std | host | notes
 `i686-unknown-haiku` | ✓ | ✓ | 32-bit Haiku [^x86_32-floats-return-ABI]
 [`i686-unknown-hurd-gnu`](platform-support/hurd.md) | ✓ | ✓ | 32-bit GNU/Hurd [^x86_32-floats-return-ABI]
 [`i686-unknown-netbsd`](platform-support/netbsd.md) | ✓ | ✓ | NetBSD/i386 with SSE2 [^x86_32-floats-return-ABI]
+[`i686-unknown-nuttx`](platform-support/nuttx.md) | ✓ |  | 32-bit x86 with NuttX
 [`i686-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | 32-bit OpenBSD [^x86_32-floats-return-ABI]
 [`i686-unknown-redox`](platform-support/redox.md) | ✓ |  | i686 Redox OS
 `i686-uwp-windows-gnu` | ✓ |  | [^x86_32-floats-return-ABI]
@@ -417,6 +418,7 @@ target | std | host | notes
 `x86_64-unknown-l4re-uclibc` | ? |  |
 [`x86_64-unknown-linux-none`](platform-support/x86_64-unknown-linux-none.md) | * |  | 64-bit Linux with no libc
 [`x86_64-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | 64-bit OpenBSD
+[`x86_64-unknown-nuttx`](platform-support/nuttx.md) | ✓ |  | 64-bit x86 with NuttX
 [`x86_64-unknown-trusty`](platform-support/trusty.md) | ? |  |
 `x86_64-uwp-windows-gnu` | ✓ |  |
 [`x86_64-uwp-windows-msvc`](platform-support/uwp-windows-msvc.md) | ✓ |  |

src/doc/rustc/src/platform-support/nuttx.md

@@ -20,6 +20,8 @@ The target name follow this format: `ARCH[-VENDOR]-nuttx-ABI`, where `ARCH` is t
 
 The following target names are defined:
 
+- `i686-unknown-nuttx`
+- `x86_64-unknown-nuttx`
 - `aarch64-unknown-nuttx`
 - `armv7a-nuttx-eabi`
 - `armv7a-nuttx-eabihf`

tests/assembly/targets/targets-elf.rs

@@ -249,6 +249,9 @@
 //@ revisions: i686_unknown_netbsd
 //@ [i686_unknown_netbsd] compile-flags: --target i686-unknown-netbsd
 //@ [i686_unknown_netbsd] needs-llvm-components: x86
+//@ revisions: i686_unknown_nuttx
+//@ [i686_unknown_nuttx] compile-flags: --target i686-unknown-nuttx
+//@ [i686_unknown_nuttx] needs-llvm-components: x86
 //@ revisions: i686_unknown_openbsd
 //@ [i686_unknown_openbsd] compile-flags: --target i686-unknown-openbsd
 //@ [i686_unknown_openbsd] needs-llvm-components: x86
@@ -627,6 +630,9 @@
 //@ revisions: x86_64_unknown_none
 //@ [x86_64_unknown_none] compile-flags: --target x86_64-unknown-none
 //@ [x86_64_unknown_none] needs-llvm-components: x86
+//@ revisions: x86_64_unknown_nuttx
+//@ [x86_64_unknown_nuttx] compile-flags: --target x86_64-unknown-nuttx
+//@ [x86_64_unknown_nuttx] needs-llvm-components: x86
 //@ revisions: x86_64_unknown_openbsd
 //@ [x86_64_unknown_openbsd] compile-flags: --target x86_64-unknown-openbsd
 //@ [x86_64_unknown_openbsd] needs-llvm-components: x86